In many situations, it is desirable to project the display of a calculator or computer onto a large screen for group viewing. In particular, it is often desirable for a teacher to operate a computing device while the display is projected onto a large screen for viewing by the entire class. Present day solutions, however, have not been effective in providing a low cost solution which is easily operated by the speaker/teacher.
One such solution is to use a calculator which has an opening in its case such that light may be transmitted through the display itself. The calculator is set upon the base of an overhead projector. Thus, the display acts as a transparency and its image may be projected to a large screen.
This approach has significant problems. First, due to the size of the calculator display, the image projected is generally too small to be comfortably viewed by the audience. Second, the base of the overhead is capable of generating significant heat, which affects the LCD display, eventually making the entire display opaque. Third, since the entire calculator sits on the base of the overhead projector, the speaker must stare into the light emitted by the base while operating the calculator.
Another approach is typically used with computers. This approach provides a liquid crystal display (LCD) pallet of about the same size as a typically transparency used on an overhead projector. The pallet is placed on the overhead projector and is driven by the computer. Because of the size of the LCD and because of the additional hardware necessary to cool the display, this alternative results in a high system cost.
Therefore, a need has arisen for a display which may be used in conjunction with an overhead projector which provides a large projected image at low cost and which is less susceptible to heat related performance degradation than prior art solutions.